Open vessel sealing instrument with cutting mechanism

ABSTRACT

An open electrosurgical forceps for sealing tissue includes a pair of first and second shaft members each having a jaw member disposed at a distal end thereof. The jaw members are movable from a first position in spaced relation relative to one another to a subsequent position wherein the jaw members cooperate to grasp tissue therebetween. Each of the jaw members includes an electrically conductive sealing plate for communicating electrosurgical energy through tissue held therebetween. At least one of the jaw members includes a cutting slot defined along a length thereof which is dimensioned to reciprocate a cutting instrument therealong for cutting tissue disposed between jaw members. An actuator advances the cutting instrument from a first position wherein the cutting instrument is disposed proximal to tissue held between the jaw members to at least one subsequent position wherein the cutting instrument is disposed distal to tissue held between the jaw members.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/546,838 filed Oct. 12, 2006, now U.S. Pat. No. 7,922,718, which is acontinuation of and claims the benefit of priority to U.S. applicationSer. No. 10/991,157 filed Nov. 17, 2004, now U.S. Pat. No. 7,131,970,which claims the benefit of priority to U.S. Provisional ApplicationSerial No. 60/523,387 filed on Nov. 19, 2003, the entire contents ofeach of which is incorporated herein by reference.

BACKGROUND

The present disclosure relates to forceps used for open surgicalprocedures. More particularly, the present disclosure relates to an openforceps which applies a combination of mechanical clamping pressure andelectrosurgical energy to seal tissue and a knife which is selectivelyactivateable to sever tissue.

TECHNICAL FIELD

A forceps is a plier-like instrument which relies on mechanical actionbetween its jaws to grasp, clamp and constrict vessels or tissue.So-called “open forceps” are commonly used in open surgical procedureswhereas “endoscopic forceps” or “laparoscopic forceps” are, as the nameimplies, used for less invasive endoscopic surgical procedures.Electrosurgical forceps (open or endoscopic) utilize both mechanicalclamping action and electrical energy to effect hemostasis by heatingtissue and blood vessels to coagulate and/or cauterize tissue.

Certain surgical procedures require more than simply cauterizing tissueand rely on the unique combination of clamping pressure, preciseelectrosurgical energy control and gap distance (i.e., distance betweenopposing jaw members when closed about tissue) to “seal” tissue, vesselsand certain vascular bundles.

Vessel sealing or tissue sealing is a recently-developed technologywhich utilizes a unique combination of radio frequency energy, pressureand gap control to effectively seal or fuse tissue between two opposingjaw members or sealing plates. Vessel or tissue sealing is more than“cauterization” which is defined as the use of heat to destroy tissue(also called “diathermy” or “electrodiathermy”) and vessel sealing ismore than “coagulation” which is defined as a process of desiccatingtissue wherein the tissue cells are ruptured and dried. “Vessel sealing”is defined as the process of liquefying the collagen, elastin and groundsubstances in the tissue so that it reforms into a fused mass withsignificantly-reduced demarcation between the opposing tissuestructures.

In order to effectively “seal” tissue or vessels, two predominantmechanical parameters must be accurately controlled: 1) the pressureapplied to the vessel or tissue; and 2) the gap distance between theconductive tissue contacting surfaces (electrodes). As can beappreciated, both of these parameters are affected by the thickness ofthe tissue being sealed. Accurate application of pressure is importantfor several reasons: to reduce the tissue impedance to a low enoughvalue that allows enough electrosurgical energy through the tissue; toovercome the forces of expansion during tissue heating; and tocontribute to the end tissue thickness which is an indication of a goodseal. It has been determined that a good seal for certain tissues isoptimum between 0.001 inches and 0.006 inches.

With respect to smaller vessels or tissue, the pressure applied becomesless relevant and the gap distance between the electrically conductivesurfaces becomes more significant for effective sealing. In other words,the chances of the two electrically conductive surfaces touching duringactivation increases as the tissue thickness and the vessels becomesmaller.

Commonly owned, U.S. Pat. No. 6,511,480, PCT Patent Application Nos.PCT/US01/11420 and PCT/US01/11218, U.S. patent applications Ser. Nos.10/116,824, 10/284,562 and 10/299,650 all describe various open surgicalforceps which seal tissue and vessels. All of these references arehereby incorporated by reference herein. In addition, several journalarticles have disclosed methods for sealing small blood vessels usingelectrosurgery. An article entitled Studies on Coagulation and theDevelopment of an Automatic Computerized Bipolar Coagulator, J.Neurosurg., Volume 75, July 1991, describes a bipolar coagulator whichis used to seal small blood vessels. The article states that it is notpossible to safely coagulate arteries with a diameter larger than 2 to2.5 mm. A second article is entitled Automatically Controlled BipolarElectrocoagulation—“COA-COMP”, Neurosurg. Rev. (1984), pp. 187-190,describes a method for terminating electrosurgical power to the vesselso that charring of the vessel walls can be avoided.

Typically and particularly with respect to open electrosurgicalprocedures, once a vessel is sealed, the surgeon has to remove thesealing instrument from the operative site, substitute a new instrumentand accurately sever the vessel along the newly formed tissue seal. Ascan be appreciated, this additional step may be both time consuming(particularly when sealing a significant number of vessels) and maycontribute to imprecise separation of the tissue along the sealing linedue to the misalignment or misplacement of the severing instrument alongthe center of the tissue sealing line.

Many endoscopic vessel sealing instruments have been designed whichincorporate a knife or blade member which effectively severs the tissueafter forming a tissue seal. For example, commonly-owned U.S.application Ser. Nos. 10/116,944 and 10/179,863 describe one suchendoscopic instrument which effectively seals and cuts tissue along thetissue seal. Other instruments include blade members or shearing memberswhich simply cut tissue in a mechanical and/or electromechanical mannerand are relatively ineffective for vessel sealing purposes.

There exists a need to develop an open electrosurgical forceps which issimple, reliable and inexpensive to manufacture and which effectivelyseals tissue and vessels and which allows a surgeon to utilize the sameinstrument to effectively sever the tissue along the newly formed tissueseal.

SUMMARY

The present disclosure relates to an open electrosurgical forceps forsealing tissue and includes a pair of first and second shaft memberseach having a jaw member disposed at a distal end thereof. The jawmembers are movable from a first position in spaced relation relative toone another to at least one subsequent position wherein the jaw memberscooperate to grasp tissue therebetween. Each of the jaw members includesan electrically conductive sealing plate or sealing surface on an innerfacing surface which communicates electrosurgical energy through tissueheld therebetween. Preferably, one of the jaw members includes a cuttingslot defined along a longitudinal length thereof which is dimensioned toreciprocate a cutting instrument therealong to sever tissue held betweenthe jaw members. An actuator is included for selectively advancing thecutting instrument from a first position wherein the cutting instrumentis disposed proximal to tissue held between the jaw members to at leastone subsequent position wherein the cutting instrument is disposeddistal to tissue held between the jaw members.

In one embodiment, the actuator includes a trigger assembly whichcooperates with a pulley and cable system to advance the cuttinginstrument from the first to second positions through tissue heldtherebetween. The trigger assembly of the actuator may be movedproximally, distally or laterally to distally advance the cuttinginstrument through the cutting slot.

Preferably, the forceps includes a safety mechanism or lockout toprevent reciprocation of the cutting instrument when the jaws aredisposed in the first position. The lock out may form part of thetrigger assembly and/or part of one or both of the jaw assemblies.

In one embodiment, each of the shafts includes a handle and at least oneof the handle defines a track therethrough for reciprocating a cable ofthe pulley and cable system. The cable is mechanically engaged with thecutting instrument such that movement of the cable imparts movement ofthe cutting instrument between the first and subsequent positions.Preferably, the cable is manufactured from a plastic or braided flexiblematerial and may include one or more stiffeners to prevent the cablefrom buckling within the track.

In another embodiment, the forceps includes one or more springs whichautomatically bias the cutting instrument in the first position suchthat after the cutting instrument severs the tissue held between the jawmembers, the cutting instrument automatically returns to the firstposition. Preferably, the trigger assembly includes at least one springfor automatically returning the cutting instrument back to the firstposition.

In another embodiment, the actuator includes a trigger assembly whichcooperates with a rack and pinion system to advance the cuttinginstrument from the first to second positions through tissue heldtherebetween. Preferably, the rack and pinion system is engaged with oneof the first and second shaft members. The trigger assembly of theactuator may be moved proximally, distally or laterally to distallyadvance the cutting instrument through the cutting slot.

The present invention also relates to an open electrosurgical forcepsfor sealing tissue which includes a pair of first and second shaftmembers each having a jaw member disposed at a distal end thereof. Thejaw members are movable from a first position in spaced relationrelative to one another to a subsequent position wherein the jaw memberscooperate to grasp tissue therebetween. One of the shaft membersincludes a flange that mechanically interfaces with a correspondingopening defined within the other of the shaft members. Each of the jawmembers includes an electrically conductive sealing plate forcommunicating electrosurgical energy through tissue held therebetween.At least one of the jaw members includes a cutting slot defined along alength thereof that is dimensioned to reciprocate a cutting instrumenttherealong. An actuator is included which selectively reciprocates thecutting instrument to cut tissue disposed between the jaw members. Alockout is also included which has a spring biased within the openingdefined in the corresponding shaft member to prevent reciprocation ofthe cutting instrument when the jaw members are disposed in the firstposition. The spring is disengaged by the flange when the jaw membersare moved to the second position.

In one embodiment, the flange includes an aperture defined therein whichallows reciprocation of a safety bar of the cutting instrumenttherethrough when the jaw members are moved to the second position. Thelockout is preferably disposed within a proximal end of the forceps andthe spring is configured to disengage into a chamber recessed within thecorresponding shaft member.

In another embodiment according to the present disclosure, a forceps isprovided which includes a lockout mechanism having a notch definedwithin a portion of the cutting instrument. The notch is configured tomechanically engage a corresponding detent on the pivot to preventreciprocation of the cutting instrument when the jaw members aredisposed in the first position. The notch automatically disengages fromthe detent when the jaw members are moved to the second position topermit selective reciprocation of the cutting instrument. The notch maybe defined within a drive rod of the cutting instrument.

Still another embodiment of the present disclosure relates to an openelectrosurgical forceps for sealing tissue having a pair of first andsecond shaft members each having a jaw member disposed at a distal endthereof. The jaw members are movable about a pivot from a first positionin spaced relation relative to one another to a subsequent positionwherein the jaw members cooperate to grasp tissue therebetween. Each ofthe jaw members is curved relative to a longitudinal axis definedthrough the shaft members and each jaw member includes a correspondinglycurved electrically conductive sealing plate which communicateselectrosurgical energy through tissue held therebetween. One (or both)of the jaw members includes a substantially curved cutting slot definedalong a length thereof which is dimensioned to reciprocate asubstantially flexible cutting instrument therealong via an actuator. Alockout operatively couples to the cutting instrument and is configuredto prevent reciprocation of the cutting instrument when the jaw membersare disposed in the first position.

In yet still another embodiment, one (or both) of the jaw members mayinclude a substantially straight cutting slot defined along a lengththereof which is dimensioned to reciprocate a cutting instrumenttherealong via an actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the subject instrument are described herein withreference to the drawings wherein:

FIG. 1A is a left, perspective view of an open forceps according to thepresent disclosure;

FIG. 1B is a left, side view of the forceps of FIG. 1A;

FIG. 1C is an internal view of the forceps of FIG. 1A showing a rack andpinion actuating mechanism for advancing a cutting knife;

FIG. 1D is an internal, perspective view of an alternate embodiment ofthe open forceps according to the present disclosure having a rack andpinion actuating mechanism for advancing the cutting knife;

FIG. 1E is an enlarged, perspective view showing the distal end of theactuating mechanism which attaches to the cutting knife;

FIG. 2A is a left, perspective view of an alternate embodiment of anopen forceps according to the present disclosure;

FIG. 2B is a left, side view of the forceps of FIG. 2A;

FIG. 2C is an internal view of the forceps of FIG. 2A showing a flexiblelinkage actuating mechanism for advancing the cutting knife;

FIG. 2D is an internal view of the forceps of FIG. 2A showing a flexiblewire actuating mechanism for advancing the cutting knife;

FIG. 2E is a side, internal view of the trigger for advancing andretracting the flexible wire of FIG. 2D;

FIG. 3 is a perspective view of an alternate embodiment of the openforceps according to the present disclosure having a forwardlyactivateable actuating mechanism for advancing the cutting knife;

FIG. 4 is a perspective view of an alternate embodiment of the openforceps according to the present disclosure having a lever arm whichadvances the cutting knife;

FIG. 5A is an internal, side view of a forceps according to the presentdisclosure showing an electrosurgical cable and the various internalelectrical connections therein;

FIG. 5B is a cross section of the electrosurgical cable taken along line5B-5B of FIG. 5A;

FIG. 5C is a side view of the electrosurgical cable with part of theouter insulative sheathing removed;

FIG. 6A is an enlarged view of a safety mechanism according to thepresent disclosure shown in a disengaged position;

FIG. 6B is a greatly-enlarged view of the safety mechanism of FIG. 6A;

FIG. 6C is a greatly-enlarged view of the safety mechanism of FIG. 6Ashown being activated;

FIG. 6D is a greatly-enlarged view of the safety mechanism of FIG. 6A inan activated position to allow reciprocation of the actuating mechanism;

FIG. 6E is a greatly-enlarged view of another embodiment of a safetymechanism or lockout which may be utilized with any of the aboveembodiments of the open forceps described above;

FIG. 6F is a greatly-enlarged view of a knife carrier for use with thesafety mechanism of FIG. 6E; and

FIG. 7 is an enlarged, top view showing a cutting knife which isgenerally disposed off-axis relative to the distal end of the forceps tofacilitate tissue cutting around a curved jaw member.

DETAILED DESCRIPTION

Referring now to FIGS. 1A-1E, a forceps 10 for use with open surgicalprocedures includes elongated shaft portions 12 and 20 each having aproximal end 14 and 24, respectively, and a distal end 16 and 26,respectively. In the drawings and in the descriptions which follow, theterm “proximal”, as is traditional, will refer to the end of the forceps10 which is closer to the user, while the term “distal” will refer tothe end which is further from the user.

The forceps 10 includes an end effector assembly 60 which attaches tothe distal ends 16 and 26 of shafts 12 and 20, respectively. Asexplained in more detail below, the end effector assembly 60 includespair of opposing jaw members 62 and 64 which are pivotably connectedabout a pivot pin 65 and which are movable relative to one another tograsp tissue.

Preferably, each shaft 12 and 20 includes a handle 15 and 17, disposedat the proximal end 14 and 24 thereof which each define a finger hole 15a and 17 a, respectively, therethrough for receiving a finger of theuser. As can be appreciated, finger holes 15 a and 17 a facilitatemovement of the shafts 12 and 20 relative to one another which, in turn,pivot the jaw members 62 and 64 from an open position wherein the jawmembers 62 and 64 are disposed in spaced relation relative to oneanother to a clamping or closed position wherein the jaw members 62 and64 cooperate to grasp tissue therebetween.

As best seen in FIG. 1A, shaft 20 is bifurcated to define an elongatedchannel 21 therealong which is dimensioned to receive shaft 12 therein.More particularly, shaft 20 is made from two halves 20 a and 20 b whichare matingly engaged during assembly to form shaft 20 and to define theelongated channel 21. It is envisioned that the two halves 20 a and 20 bmay be sonic-welded together at a plurality of different weld points 75or the housing halves may be mechanically engaged in any other knownfashion, snap-fit, glued, screwed, etc. Upon assembly, shaft 12 ispositioned within shaft 20 and secured about pivot 65 which allows thetwo shafts 12 and 20 to pivot with respect to one another. When the usermoves the shaft 12 relative to shaft 20 to close the jaw members 62 and64, shaft 12 is received within the elongated channel 21 of shaft 20. Itis envisioned that configuring the two shafts 12 and 20 in the fashionfacilitates gripping and reduces the overall size of the forceps 10which is especially advantageous during surgeries in small cavities.

As best illustrated in FIG. 1A, one of the shafts, e.g., 20, includes aproximal shaft connector 79 which is designed to connect the forceps 10to a source of electrosurgical energy such as an electrosurgicalgenerator (not shown). The proximal shaft connector 79electromechanically engages an electrosurgical cable 70 such that theuser may selectively apply electrosurgical energy as needed.Alternatively, the cable 70 may be fed directly into shaft 20 as bestseen in FIG. 5A.

As explained in more detail below, the distal end of the cable 70connects to a handswitch 50 to permit the user to selectively applyelectrosurgical energy as need to seal tissue grasped between jawmembers 62 and 64. More particularly, the interior of cable 70 housesleads 70 a, 70 b and 70 c which upon activation of the handswitch 50conduct the different electrical potentials from the electrosurgicalgenerator to the jaw members 62 and 64. As can be appreciated,positioning the switch 50 on the forceps 10 gives the user more visualand tactile control over the application of electrosurgical energy.These aspects are explained below with respect to FIGS. 5A-5C and thediscussion of the handswitch 50 and the electrical connectionsassociated therewith.

As best seen in FIGS. 1A and 1B, the two opposing jaw members 62 and 64of the end effector assembly 60 are pivotable about pin 65 from the openposition to the closed position for grasping tissue therebetween. Jawmembers 62 and 64 are generally symmetrical and include similarcomponent features which cooperate to permit facile rotation about pivotpin 65 to effect the grasping and sealing of tissue. As a result andunless otherwise noted, jaw member 62 and the operative featuresassociated therewith are initially described herein in detail and thesimilar component features with respect to jaw member 64 will be brieflysummarized thereafter. Moreover, many of the features of the jaw members62 and 64 are described in detail in commonly-owned U.S. patentapplication Ser. Nos. 10/284,562, 10/116,824, 09/425,696, 09/178,027 andPCT Application Serial No. PCT/US01/11420 the contents of which are allhereby incorporated by reference in their entirety herein.

Jaw member 62 includes an insulated outer housing 63 which isdimensioned to mechanically engage an electrically conductive sealingsurface 67. The outer insulative housing 63 extends along the entirelength of jaw member 62 to reduce alternate or stray current pathsduring sealing and/or incidental burning of tissue. The electricallyconductive surface 67 conducts electrosurgical energy of a firstpotential to the tissue upon activation of the handswitch 50. Insulatedouter housing 63 is dimensioned to securely engage the electricallyconductive sealing surface 67. It is envisioned that this may beaccomplished by stamping, by overmolding, by overmolding a stampedelectrically conductive sealing plate and/or by overmolding a metalinjection molded seal plate. Other methods of affixing the seal surface67 to the outer housing 63 are described in detail in one or more of theabove-identified references.

It is also envisioned that the electrically conductive sealing surface67 may include a pinch trim (not shown) which facilitates secureengagement of the electrically conductive surface 67 to the insulatedouter housing 63 and also simplifies the overall manufacturing process.It is also contemplated that the electrically conductive sealing surface67 may include an outer peripheral edge which has a radius and theinsulated outer housing 63 meets the electrically conductive sealingsurface 67 along an adjoining edge which is generally tangential to theradius and/or meets along the radius. Preferably, at the interface, theelectrically conductive surface 67 is raised relative to the insulatedouter housing 63. These and other envisioned embodiments are discussedin commonly-owned, co-pending PCT Application Serial No. PCT/US01/11412and commonly owned, co-pending PCT Application Serial No.PCT/US01/11411, the contents of both of these applications beingincorporated by reference herein in their entirety.

Preferably, the insulated outer housing 63 and the electricallyconductive sealing surface 67 are dimensioned to limit and/or reducemany of the known undesirable effects related to tissue sealing, e.g.,flashover, thermal spread and stray current dissipation. All of theaforementioned and cross referenced manufacturing techniques produce anelectrode having an electrically conductive surface 67 which issubstantially surrounded by an insulated outer housing 63.

Likewise, jaw member 64 includes similar elements which include: anouter housing 66 which engages an electrically conductive sealingsurface 68. The electrically conducive sealing surface 68 conductselectrosurgical energy of a second potential to the tissue uponactivation of the handswitch 50.

It is envisioned that one of the jaw members, e.g., 62, includes atleast one stop member (not shown) disposed on the inner facing surfaceof the electrically conductive sealing surface 67 (and/or 68).Alternatively or in addition, the stop member may be positioned adjacentto the electrically conductive sealing surfaces 67, 68 or proximate thepivot pin 65. The stop member(s) is preferably designed to facilitategripping and manipulation of tissue and to define a gap “G” (FIG. 1A)between opposing jaw members 62 and 64 during sealing. Preferably theseparation distance during sealing or the gap distance “G” is within therange of about 0.001 inches (˜0.03 millimeters) to about 0.006 inches(˜0.016 millimeters).

A detailed discussion of these and other envisioned stop members as wellas various manufacturing and assembling processes for attaching,disposing, depositing and/or affixing the stop members to theelectrically conductive sealing surfaces 67, 68 are described incommonly-assigned, co-pending PCT Application Serial No. PCT/US01/11222which is hereby incorporated by reference in its entirety herein.

As mentioned above, two mechanical factors play an important role indetermining the resulting thickness of the sealed tissue andeffectiveness of the seal, i.e., the pressure applied between opposingjaw members 62 and 64 and the gap “G” between the opposing jaw members62 and 64 (or opposing seal surface 67 and 68 during activation). It isknown that the thickness of the resulting tissue seal cannot beadequately controlled by force alone. In other words, too much force andthe two jaw members 62 and 64 would touch and possibly short resultingin little energy traveling through the tissue thus resulting in a badseal. Too little force and the seal would be too thick. Applying thecorrect force is also important for other reasons: to oppose the wallsof the vessel; to reduce the tissue impedance to a low enough value thatallows enough current through the tissue; and to overcome the forces ofexpansion during tissue heating in addition to contributing towardscreating the required end tissue thickness which is an indication of agood seal.

Preferably, the seal surfaces 67 and 68 are relatively flat to avoidcurrent concentrations at sharp edges and to avoid arcing between highpoints. In addition and due to the reaction force of the tissue whenengaged, jaw members 62 and 64 are preferably manufactured to resistbending, i.e., tapered along their length which provides a constantpressure for a constant tissue thickness at parallel and the thickerproximal portion of the jaw members 62 and 64 will resist bending due tothe reaction force of the tissue.

As best seen in FIGS. 1C and 1D, the jaw members 62 and 64 include aknife channel 69 disposed therebetween which is configured to allowreciprocation of a cutting mechanism 90 therewithin. One example of aknife channel is disclosed in commonly-owned U.S. patent applicationSer. No. 10/284,562 the entire contents of which are hereby incorporatedby reference herein. Preferably, the complete knife channel 69 is formedwhen two opposing channel halves 69 a and 69 b come together upongrasping of the tissue. It is envisioned that the knife channel 69 maybe tapered or some other configuration which facilitates or enhancescutting of the tissue during reciprocation of the cutting mechanism 90in the distal direction. Moreover, the knife channel 69 may be formedwith one or more safety features which prevent the cutting mechanism 90from advancing through the tissue until the jaw members 62 and 64 areclosed about the tissue.

FIG. 1B shows a lockout mechanism 47 associated with the actuatingassembly 40 to prevent advancement of the cutting mechanism until thejaw members are positioned about tissue. Other lockout mechanisms andfeatures are described in commonly-owned U.S. application Ser. Nos.10/460,926, 10/461,550 and 10/462,121 which are all incorporated byreference herein in their entirety. FIGS. 6A-6D show another example ofa safety/lockout mechanism.

As best shown in FIGS. 1A-1D, the arrangement of shaft 12 is slightlydifferent from shaft 20. More particularly, shaft 20 is hollow to definea chamber 28 therethrough which is dimensioned to house both thehandswitch 50 (and the electrical components associated therewith asexplained in more detail below) and the actuating mechanism 40. As bestseen in FIGS. 1C and 1D, the actuating mechanism 40 includes a fingertab 42 which is operatively associated with a first gear rack 44 suchthat movement of the finger tab 42 moves the first rack 44 in acorresponding direction. The actuating mechanism 40 also includes asecond gear rack 46 which is operatively associated with a drive rod 48which advances the cutting mechanism 90 as will be explained in moredetail below. Drive rod 48 includes a distal end 49 which is configuredto mechanically support the cutting mechanism 90 (See FIG. 1E).

Distal end 49 may include one or more guide mechanisms (not shown) tocontrol or guide the cutting mechanism 90 through the knife channel 69between opposing jaw members 62 and 64. Preferably, the drive rod 48 ismade from a flexible wire or plastic sheath which does not buckle uponforward movement thereof. It is also contemplated that the drive rod mayinclude a groove or notch 43 which prevents movement thereof when thejaw members are opened relative to one another. Likewise, pivot 65 (orsome other part of forceps 10) may include a corresponding detent orprotrusion 69′ which engages the notch 43 to prevent accidental firingof the cutting mechanism 90 when the forceps 10 is disposed in the openposition.

Interdisposed between the first and second gear racks 44 and 46,respectively, is a pinion gear 45 which mechanically meshes with bothgear racks 44 and 46 and converts proximal motion of the finger tab 42into distal translation of the drive rod 48 and vice versa. Moreparticularly, when the user pulls the finger tab 42 in a proximaldirection within a predisposed channel 29 in the chamber 28 asrepresented by arrow “A”, the first rack 44 is translated proximallywhich, in turn, rotates the pinion gear 45 in a clockwise direction.Rotation of the pinion gear 45 in a clockwise direction forces thesecond rack 46 to translate the drive rod 48 distally (See arrow “B”)which advances the cutting mechanism 90 through tissue grasped betweenjaw members 62 and 64. As mentioned above, the cutting mechanism 90,e.g., knife, blade, wire, etc., is advanced through channel 69 upondistal translation of the drive rod 48.

It is envisioned that multiple gears or gears with different gear ratiosmay be employed to reduce surgical fatigue which may be associated withadvancing the cutting mechanism 90. In addition, it is contemplated thetracks 44 and 46 may be of different length to provide additionalmechanical advantage for advancing the jaw members through tissue. Asbest shown in FIG. 1C, the rack and pinion arrangement may be curved forspatial purposes and to facilitate handling and/or to enhance theoverall ergonomics of the forceps 10.

A spring 85 may be employed within chamber 28 to bias the first rack 44upon proximal movement thereof such that upon release of the finger tab42, the force of the spring 85 automatically returns the first rack 44to its distal most position within channel 29. Obviously, spring 85 maybe operatively connected to bias the second rack 46 to achieve the samepurpose.

Preferably, the finger tab 42 includes one or more ergonomicallyfriendly features which enhance the tactile feel and grip for the userto facilitate actuation of the finger tab 42. Such features may include,raised protuberances, rubber inserts, scallops and gripping surfaces andthe like.

FIG. 1D shows another embodiment of the present disclosure similar tothe embodiment of FIG. 1C which includes a ratchet 74 for selectivelylocking the jaw members 62 and 64 relative to one another at variouspositions during pivoting. A first ratchet interface 76 extends from theproximal end 14 of shaft member 12 towards a second ratchet interface 78on the proximal end 24 of shaft 20 in a generally vertically alignedmanner such that the inner facing surfaces of each ratchet 76 and 78abut one another upon closure about the tissue. Preferably, each ratchetinterface 76 and 78 includes a plurality of flanges 77 a and 77 b,respectively, which project from the inner facing surface of eachratchet interface 76 and 78 such that the ratchet interfaces 77 a and 77b interlock in at least one position. In the embodiment shown in FIG.1D, the ratchet interfaces 77 a and 77 b interlock at several differentpositions.

Preferably, each position associated with the cooperating ratchetinterfaces 77 a and 77 b holds a specific, i.e., constant, strain energyin the shaft members 12 and 20 which, in turn, transmits a specificclosing force to the jaw members 62 and 64. It is envisioned that theratchet 74 may include graduations or other visual markings which enablethe user to easily and quickly ascertain and control the amount ofclosure force desired between the jaw members.

FIG. 1D also shows a lockout mechanism 99 which is designed to preventfiring of the cutting mechanism until the jaw members 62 and 64 aremoved into closed position about tissue. As can be appreciated, thelockout 99 acts as a safety mechanism to prevent accidental severing oftissue prior to formation of a tissue seal. It is also envisioned thatthe lockout could cooperate with one or more electrical orelectromechanical sensors (not shown) which prevent the cuttingmechanism 90 from advancing through tissue until a tissue seal has beencreated. For example, the lockout 99 could include a sensor which uponcompletion of a tissue seal activates a switch or release (not shown)which unlocks the cutting mechanism 90 for advancement through tissue.

It is envisioned that by making the forceps 10 disposable, the forceps10 is less likely to become damaged since it is only intended for asingle use and, therefore, does not require cleaning or sterilization.As a result, the functionality and consistency of the vital sealingcomponents, e.g., the conductive surfaces 67 and 68, the stop member(s)150, and the insulative housings 63 and 66 will assure a uniform andquality seal.

FIGS. 2A-2E show another embodiment of the presently disclosed forceps100 which includes an alternative actuating mechanism 140 whichselectively advances the cutting mechanism 190 to separate the tissueonce sealed. More particularly, forceps 100 includes shafts 112 and 120which cooperate to move jaw members 162 and 164 from a first positionwherein the jaw members 162 and 164 are disposed in spaced relationrelative to one another to a second position wherein the jaw memberscooperate to grasp tissue therebetween. Much like the forceps 10 ofFIGS. 1A-1C, shaft 112 and shaft 120 are dimensioned to allowreciprocation of shaft 112 within the elongated channel 121 of shaft120. In addition, jaw members 162 and 164 are similar to the jaw members62 and 64 of FIGS. 1A-1C and include similar elements and features,e.g., sealing surfaces 167 and 168, outer insulative housings 163 and166 and pivot 165. Forceps 100 also includes ring handles 115 and 117which each define a corresponding finger hole 115 a and 117 a,respectively, therein to enable the user to manipulate and grasp tissuewith the jaw members 162 and 164.

Ring handle 117 includes an elongated drive path 119 definedtherethrough which extends from the chamber 129, around the ring handle117 and through the shaft 120 to the distal end of the forceps 100. Asbest seen in FIGS. 2B and 2C the finger tab 142 is slideable withinchannel 129 in a proximal direction (represented by arrow “A”) whichadvances the cutting mechanism 90 through tissue held between jawmembers 162 and 164. More particularly, the finger tab 142 is connectedto a sled-like carrier 144 which is operatively connected to a flexibleelement 148 such that movement of the carrier 144 moves the element 148.Element 148, in turn, is reciprocated within the drive path 119 andextends around the handle 117 to the distal end 116 where the distal end149 mechanically engages the cutting mechanism 90. As can beappreciated, proximal movement of the finger tab 142 moves the flexibleelement 148 within the drive path 119 around the handle 117 whichdistally advances the cutting mechanism 90 through tissue. It isenvisioned that designing the forceps 100 to have the driving flexibleelement 148 advance around the ring handle 117 provides maximum spatialbenefit and facilitates handling of the forceps 100. A spring 185 may beemployed to bias the finger tab 142 in a distal-most position andautomatically return the finger tab 142 after deployment.

It is envisioned that the actuating mechanism 140 could be configuredutilizing one or more pulleys 225 (See FIG. 2E) to facilitatetranslation of the flexible element 148 through the tissue. In addition,it is contemplated that the actuating mechanism 140 can be configuredsuch that distal movement of the finger tab 142 advances the flexibleelement 148 in a distal direction to cut tissue utilizing one or morepulleys (See FIG. 2E).

FIG. 2C preferably utilizes a flexible plastic sheath or flexiblelinkage as the flexible element 148 to advance the cutting mechanism 90.It is envisioned that the flexible linkage prevents buckling duringactivation. However and as best seen in FIG. 2D, a flexible wire may beutilized in lieu of the flexible plastic sheath. Wire 248 operates in asimilar fashion as the plastic flexible sheath 148 of FIG. 2C such thatupon movement of the finger tab 142 the flexible wire 248 advances thecutting mechanism 90 through tissue held between jaw members 162 and164.

FIGS. 5A-5C show the electrical details relating to the switch 50. Moreparticularly and as mentioned above, cable 70 includes three electricalleads 70 a, 70 b and 70 c which are fed through shaft 20. Theelectrosurgical cable 70 is fed into the bottom of shaft 20 and is heldsecurely therein by one or more mechanical interfaces (not shown). Lead70 c extends directly from cable 70 and connects to jaw member 64 toconduct the second electrical potential thereto. Leads 70 a and 70 bextend from cable 70 and connect to the hand switch or joy-stick-liketoggle switch 50 (or 150 in FIG. 2A).

Several different types of handswitches 50 are envisioned, for example,switch 50 is a regular push-button style switch while switch 150 of FIG.2A is more like a toggle switch. It is envisioned that a toggle switch150 permits the user to selectively activate the forceps 10 in a varietyof different orientations, i.e., multi-oriented activation, whichsimplifies activation. One particular type of handswitch is disclosed incommonly-owned, co-pending U.S. patent application Ser. No. 10/460,926the contents of which are hereby incorporated by reference herein.

The electrical leads 70 a and 70 b are electrically connected to theswitch 50 (or 150). When the switch 50 is depressed, a trigger lead 71carries the first electrical potential from the switch 50 to jaw member62. As mentioned above, the second electrical potential is carried bylead 70 c directly from the generator (not shown) to jaw member 64. Itis envisioned that a safety switch or circuit (not shown) may beemployed such that the switch 50 cannot fire unless the jaw members 62and 64 are closed and/or unless the jaw members 62 and 64 have tissueheld therebetween. In the latter instance, a sensor (not shown) may beemployed to determine if tissue is held therebetween. In addition, othersensor mechanisms may be employed which determine pre-surgical,concurrent surgical (i.e., during surgery) and/or post surgicalconditions. The sensor mechanisms may also be utilized with aclosed-loop feedback system coupled to the electrosurgical generator toregulate the electrosurgical energy based upon one or more pre-surgical,concurrent surgical or post surgical conditions. Various sensormechanisms and feedback systems are described in commonly-owned,co-pending U.S. patent application Ser. No. 10/427,832 the entirecontents of which are hereby incorporated by reference herein.

Preferably, the jaw members 62 and 64 are electrically isolated from oneanother such that electrosurgical energy can be effectively transferredthrough the tissue to form a tissue seal. Preferably, each jaw member,e.g., 62, includes a uniquely-designed electrosurgical cable pathdisposed therethrough which transmits electrosurgical energy to theelectrically conductive sealing surface 67. It is envisioned that jawmember 62 may include one or more cable guides or crimp-like electricalconnectors to direct cable lead 71 towards electrically conductivesealing surface 67. Preferably, cable lead 71 is held loosely butsecurely along the cable path to permit pivoting of the jaw member 62about pivot 65.

As best shown in FIGS. 5B and 5C, the cable leads 70 a, 70 b and 70 care protected by two insulative layers, an outer protective sheath 76which surrounds all three leads 70 a, 70 b and 70 c and a secondaryprotective sheath 75 a, 75 b and 75 c which surrounds each individualcable lead, 70 a, 70 b and 70 c, respectively. The two electricalpotentials are isolated from one another by virtue of the insulativesheathing surrounding each cable lead 70 a, 70 b and 70 c.

FIG. 3 shows yet another embodiment of the forceps 300 according to thepresent disclosure wherein the actuating mechanism 340 includes a slideswitch 342 which advances the cutting mechanism 90 (not shown in thisfigure) through tissue grasped between opposing jaw members 362 and 364.More particularly, the slide switch 342 is pushed distally withinchannel 329 disposed in the shaft 320 by the surgeon to selectivelysever tissue once sealed. The switch 342 may include a bias member orspring 343 which automatically returns the cutting mechanism onceadvanced in a distal direction, i.e., automatic return. Other biasingmembers are also contemplated which are known in the art, e.g.,elastomeric bands, pulleys, etc.

Alternatively, the actuating mechanism 340 may be spring-loaded andadvanced automatically when switch 342 is depressed by the surgeon.After deployment, the surgeon manually retracts the switch 342 to resetthe switch 342 and cutting mechanism 90 for subsequent deployment.

FIG. 4 shows yet another embodiment of the presently disclosed forceps400 which includes a lever-like actuator 440 which is designed toadvance the cutting mechanism 90 through tissue grasped between jawmembers 462 and 464. More particularly, actuating mechanism 440 includesa finger tab 442 which is positioned for actuation by the user and whichis connected to a proximal end of a first link 444. Link 444 is, inturn, connected at a distal end thereof to one end of a pivot lever 445.Pivot lever 445, in turn, is connected at the opposite end thereof to asecond link 446 which connects to the cutting mechanism 90.

Pivot lever 445 is rotatably connected about a pivot pin 447 to shaft420 such that movement of the finger tab 442 and link 444 in a proximaldirection distally advances link 446 in a distal direction to move thecutting mechanism 90 through tissue. A spring (not shown) may beincluded to automatically return the finger tab 442 to its distal-mostposition after cutting. Alternatively, a third ring handle (not shown)may be employed in lieu of the finger tab 442 to advance link 444 toactuate the pivot lever 445.

As mentioned above, the knife channel 69 may be formed with a lockout orone or more other safety features which prevent the knife 90 fromadvancing through the tissue until the jaw members 62 and 64 are closedabout the tissue. As best seen in FIGS. 6A-6D, one possible lockout orsafety mechanism 505 is envisioned which both prevents actuation of thecutting blade 90 when the jaw members 62 and 64 are disposed in an openconfiguration and also prevents opening of the jaw members 62 and 64when the actuating mechanism 40 is being deployed to advance the cuttingblade 90.

More particularly, the shaft 520 and respective handle 517 may beconfigured to include an elongated channel 529 disposed therethroughwhich allows reciprocation of a safety bar 527 therein. Although shownas generally an elongated channel, it is envisioned that the channel 529may be circular or curved to accomplish the same purpose. Channel 529 iscomposed of two channel halves 529 a and 529 b disposed in horizontalregistry with one another and which are separated by an opening 537therebetween.

A leaf spring 525 (or the like) is disposed within a chamber 523 definedin the handle 517 and is moveable within the chamber 523 from a firstposition wherein the spring 525 is biased to block opening 537 to asecond position wherein the spring 525 is forced out of opening 537 toallow reciprocation of the safety bar 527. Handle 515 includes a flange513 which extends upwardly towards handle 517 and which includes anaperture 519 defined therein which is dimensioned to receive the safetybar 527 therethrough. The flange 513 is designed to be in verticalregistration with opening 537.

In use, as the jaw members 62 and 64 grasp tissue (move from the firstto second positions), the flange 513 is forced into opening 537 todislodge the spring 525 out of the opening 537 and into chamber 523.When the spring 525 is at least substantially incorporated into chamber523, the aperture 519 will align with the elongated channels 529 a and529 b (See FIG. 6C). As mentioned above, a ratchet may be employed tohold the two handles 515 and 517 together with the appropriate closureforce for sealing tissue. At this point, the user is free to activatethe actuating mechanism 40 to advance the cutting blade 90 which as bestseen in FIG. 6D translates the safety bar 527 proximally and throughaperture 513 and into elongated channel 529 b. As can be appreciated,the user is prevented from advancing the cutting blade 90 until the jawmembers 62 and 64 are closed about tissue. Moreover, when the actuatingmechanism 40 is activated, the handles 515 and 517 are locked and cannotbe opened until the actuating mechanism 40 is released.

FIGS. 6E and 6F show another version of a safety or lockout mechanism700 which acts to prevent the cutting blade 90 from being distallyactivated when the forceps is disposed in an open configuration, i.e.,the jaw members 62 and 64 are spaced relative to one another. Moreparticularly, lockout mechanism 700 is designed of two components whichmechanically cooperate to prevent accidental blade advancement, namely,a cutting blade carrier 749 and a blade lockout slot 715. Cutting bladecarrier 749 is configured to mechanically support the cutting blade 90for advancement through tissue held between the jaw members 62 and 64and preferably includes a detent or protrusion 720 which extends from atleast one side thereof. The lockout slot 715 is preferably disposed in aproximal portion of jaw member 64 near the jaw pivot 165.

When the jaw members 62 and 64 are closed about tissue, the detent 720is freely extendible within a blade slot 730 disposed within at leastone of the jaw members, e.g., jaw member 64, to cut tissue. Preferably,a return spring (not shown) automatically returns the cutting blade 90once the user releases the actuator 40. When the jaw members 62 and 64are disposed in an open configuration, the detent 720 rotates intolockout slot 715 thus preventing distal reciprocation of the cuttingblade 90 when the actuator 40 is actuated. A guide notch 725 may bepositioned within slot 730 to facilitate entry of the detent 720 intolockout slot 715.

FIG. 7 shows an alternate embodiment of the cutting mechanism 690 whichis distally advanceable to cut tissue disposed between the jaw members662 and 664. More particularly, cutting mechanism 690 is designed toinclude a cutting blade 695 which is distally advance above by a driverod 648 through a curved knife slot 669 disposed between jaw members 662and 664. The drive rod 648 and the cutting blade 695 are positionedslightly off-axis to allow for blade 695 to easily move within curvedslot 669. In other words, the distal end of the instrument includes alongitudinal axis “AA” defined therethrough and the drive rod 648 ispositioned at an angle a relative to the longitudinal axis “AA”. As canbe appreciated, positioning the drive rod “off-axis” enables the cuttingblade 695 to move more easily move through the knife channel 669 to cuttissue disposed between the jaw members 662 and 664. It is envisionedthat the jaw members 662 and 664 and/or the drive rod 648 may include asafety which prevents the blade 695 from reciprocating in the knifechannel 669 when the jaw members 662 and 664 are disposed in an openconfiguration about pivot 665.

In operation, the surgeon simply utilizes the two opposing handlemembers 15 and 17 to approximate and grasp tissue between jaw members 62and 64. The surgeon then activated the handswitch (or footswitch ifapplicable) to provide electrosurgical energy to each jaw members tocommunicate energy through the tissue held therebetween. Once sealed thesurgeon activates the actuating mechanism 40 to advance the cuttingblade 90 through the tissue to sever the tissue along the tissue seal.

From the foregoing and with reference to the various figure drawings,those skilled in the art will appreciate that certain modifications canalso be made to the present disclosure without departing from the scopeof the same. For example, although the electrical connections arepreferably incorporated within one shaft 20 and the forceps is intendedfor right-handed use, it is contemplated the electrical connections maybe incorporated within the other shaft 12 depending upon a particularpurpose and/or to facilitate manipulation by a left-handed user.

It is also contemplated that the forceps 10 (and/or the electrosurgicalgenerator used in connection with the forceps 10) may include a sensoror feedback mechanism (not shown) which automatically selects theappropriate amount of electrosurgical energy to effectively seal theparticularly-sized tissue grasped between the jaw members 62 and 64. Thesensor or feedback mechanism may also measure the impedance across thetissue during sealing and provide an indicator (visual and/or audible)that an effective seal has been created between the jaw members 62 and64. Commonly-owned U.S. patent application Ser. No. 10/427,832 disclosesseveral different types of sensory feedback mechanisms and algorithmswhich may be utilized for this purpose. The contents of this applicationare hereby incorporated by reference herein.

Experimental results suggest that the magnitude of pressure exerted onthe tissue by the sealing surfaces of the jaw members 62 and 64 areimportant in assuring a proper surgical outcome. Tissue pressures withina working range of about 3 kg/cm² to about 16 kg/cm² and, preferably,within a working range of 7 kg/cm² to 13 kg/cm² have been shown to beeffective for sealing arteries and vascular bundles. Tissue pressureswithin the range of about 4 kg/cm² to about 6.5 kg/cm² have proven to beparticularly effective in sealing arteries and tissue bundles.

In one embodiment, the shaft 12 and 20 are manufactured such that thespring constant of the shaft portions 12 a and 12 b, in conjunction withthe placement of the ratchet interfaces 32 a and 32 b, will yieldpressures within the above working range. In addition, the successivepositions of the ratchet interfaces increase the pressure betweenopposing sealing surfaces incrementally within the above working range.

It is also envisioned that the drive rod 48 may be connected to the sameor alternate source of electrosurgical energy and may be selectivelyenergizable by the surgeon during cutting. As can be appreciated, thiswould enable the surgeon to electrosurgically cut the tissue along thetissue seal. As a result thereof, a substantially dull blade may beemployed to electrosurgically cut the tissue.

It is also envisioned that a substantially dull blade may be utilizedwith a spring loaded cutting mechanism which, due to the clampingpressure between the opposing jaw members 62 and 64 and due to the forceat which the spring-loaded cutting mechanism advances the cutting blade,the tissue will sever along the tissue seal.

In one embodiment, a sealing and cutting mechanism is utilized which isselectively attachable to a conventional forceps. In other words, thesealing and cutting mechanism is disposable and the shaft members 12 and20 are reposable. The disposable sealing and cutting mechanism alongwith their respective electrosurgical elements simply mount atop one orboth shafts of a conventional forceps to enable the surgeon to seal andcut tissue. Once the surgeon is finished with the operation, the sealingand cutting mechanism is simply detached and discarded.

In one embodiment, a flexible blade may be used with a one or more ofthe above cutting mechanisms to advance through a curved knife channel.For example, upon distal advancement of the cutting mechanism, thecutting blade will simply flex and ride around the knife channel throughthe tissue held between jaw members. Alternatively, a curved blade maybe utilized which has a similar radius of curvature as the knife channelsuch that the blade will travel through the knife slot withoutcontacting the surfaces of the knife channel.

It is also contemplated that the blade 90 and blade slot 730 (See FIG.6E) may be positioned in offset relation to the pivot 165 to facilitatemanufacturing and assembly of the forceps 10. In other words, the pivot165 is radially or laterally offset from the longitudinal axis “A”disposed through the forceps 10. In this embodiment, the offsetconfiguration of the pivot 165 enables the blade 90 to be manufacturedin a generally straight configuration which does not interfere with thepivot 165 during distal activation thereof. Likewise, the blade slot 730may be configured generally straight as well.

It is also contemplated that the forceps may include a safety bladereturn mechanism (not shown). For example and as mentioned above, thecutting blade 90 may include one or more springs which automaticallyreturn the cutting blade after actuation of the actuator. In addition, amanual return may be included which allows the user to manually returnthe blade 90 if the automatic blade return (e.g., spring) should faildue to sticking, skewing, or some other unforeseen surgical condition.For example, a second pulley (not shown) may be employed opposite theactuating mechanism 40 which allows the user to manually retract theblade 90 should an automatic return (spring) fail. As can beappreciated, this second pulley (or series of pulleys if needed) wouldbe connected to the cutting blade 90 and would operate to facilitatemanual retraction as needed during the operation.

While several embodiments of the disclosure have been shown in thedrawings, it is not intended that the disclosure be limited thereto, asit is intended that the disclosure be as broad in scope as the art willallow and that the specification be read likewise. Therefore, the abovedescription should not be construed as limiting, but merely asexemplifications of preferred embodiments. Those skilled in the art willenvision other modifications within the scope and spirit of the claimsappended hereto.

1. An open electrosurgical forceps for sealing tissue, comprising: apair of first and second shaft members each having a jaw member disposedat a distal end thereof, the shaft members movable relative to eachother to move the jaw members about a pivot from a first position inspaced relation relative to one another to at least one subsequentposition wherein the jaw members cooperate to grasp tissue therebetween;each of said jaw members including an electrically conductive sealingsurface for communicating electrosurgical energy through tissue heldtherebetween; at least one of the jaw members including a cutting slotdefined along a length thereof, the cutting slot configured toaccommodate reciprocation of a cutting instrument therethrough; anactuator operably coupled to one of the first and second shaft membersfor selectively advancing the cutting instrument from a first positionwherein the cutting instrument is disposed proximal to tissue heldbetween the jaw members to at least one subsequent position wherein thecutting instrument is disposed distal to tissue held between the jawmembers, wherein upon movement of the jaw members to the at least onesubsequent position to grasp tissue therebetween, the shaft members arefurther moveable toward each other to at least one of a plurality ofpositions corresponding to a specific closing force between the jawmembers; and a lockout formed on a part of at least one of the jawmembers, the lockout configured to engage the cutting instrument toprevent advancement of the cutting instrument through tissue.
 2. An openforceps according to claim 1, wherein the lockout is formed on thepivot, the cutting instrument configured to engage the pivot when thejaw members are in the open position to prevent advancement of thecutting instrument through tissue.
 3. An open forceps according to claim2, wherein the pivot includes a detent disposed thereon configured toengage a corresponding notch disposed in the cutting instrument when thejaw members are in the open position to prevent advancement of thecutting instrument through tissue.
 4. An open forceps according to claim2, wherein the cutting instrument is configured to disengage the pivotwhen the jaw members are in the at least one subsequent position topermit advancement of the cutting instrument through tissue.
 5. An openforceps according to claim 1, wherein the cutting instrument is advancedfrom the first position to the at least one subsequent position at anangle relative to a longitudinal axis defined by at least one of theshaft members.
 6. An open forceps according to claim 1, wherein theplurality of positions are successive positions that increase a closurepressure between the electrically conductive sealing surfaces.
 7. Anopen forceps according to claim 1, wherein each shaft member includes aratchet interface disposed thereon that cooperates with a correspondingratchet interface of the opposing shaft member to interlock the shaftmembers at the at least one position upon movement of the shaft memberstoward each other.
 8. An open forceps according to claim 7, wherein theratchet interfaces abut one another upon movement of the jaw members tothe at least one subsequent position.
 9. An open forceps according toclaim 7, wherein each ratchet includes a plurality of flanges projectingfrom inner facing surface thereof that cooperate to interlock the shaftmembers in the at least one position.
 10. An open forceps according toclaim 1, wherein at least one of the shaft members includes a visualindicator corresponding to the specific closing force between the jawmembers.
 11. An open forceps according to claim 1, wherein the at leastone position of the shaft members corresponds to a specific strainenergy in the shaft members that corresponds to the specific closingforce between the jaw members.
 12. An open forceps according to claim 1,wherein at least one of the shaft members is resiliently deformable toenable movement of the shaft members toward each other to the at leastone of the plurality of positions corresponding to a specific closingforce between the jaw members.
 13. An open forceps according to claim 1,wherein a spring constant of at least one of the shaft members enablesmovement of the shaft members toward each other to the at least one of aplurality of positions corresponding to a specific closing force betweenthe jaw members.
 14. An open electrosurgical forceps for sealing tissue,comprising: a pair of first and second shaft members each having a jawmember disposed at a distal end thereof, the shaft members movablerelative to each other to move the jaw members about a pivot from afirst position in spaced relation relative to one another to at leastone subsequent position wherein the jaw members cooperate to grasptissue therebetween; each of said jaw members including an electricallyconductive sealing surface for communicating electrosurgical energythrough tissue held therebetween; at least one of the jaw membersincluding a cutting slot defined along a length thereof, the cuttingslot configured to accommodate reciprocation of a cutting instrumenttherethrough; an actuator operably coupled to one of the first andsecond shaft members for selectively advancing the cutting instrumentfrom a first position wherein the cutting instrument is disposedproximal to tissue held between the jaw members to at least onesubsequent position wherein the cutting instrument is disposed distal totissue held between the jaw members, wherein upon movement of the jawmembers to the at least one subsequent position to grasp tissuetherebetween, the shaft members are further moveable toward each otherto at least one of a plurality of positions corresponding to a specificclosing force between the jaw members; and a lockout operably coupled tothe cutting instrument and forming part of the pivot, wherein thecutting instrument operably engages the pivot when the jaw members arein the open position to prevent advancement of the cutting instrumentthrough tissue.
 15. An open forceps according to claim 14, wherein thepivot includes a detent disposed thereon configured to engage acorresponding notch disposed in the cutting instrument when the jawmembers are in the open position to prevent advancement of the cuttinginstrument through tissue.
 16. An open forceps according to claim 14,wherein the cutting instrument operably disengages the pivot when thejaw members are in the at least one subsequent position to permitadvancement of the cutting instrument through tissue.
 17. An openforceps according to claim 14, wherein the cutting instrument isadvanced from the first position to the at least one subsequent positionat an angle relative to a longitudinal axis defined by at least one ofthe shaft members.
 18. An open electrosurgical forceps for sealingtissue, comprising: a pair of first and second shaft members each havinga jaw member disposed at a distal end thereof, the shaft members movablerelative to each other to move the jaw members about a pivot from afirst position in spaced relation relative to one another to at leastone subsequent position wherein the jaw members cooperate to grasptissue therebetween, wherein upon movement of the jaw members to the atleast one subsequent position to grasp tissue therebetween, the shaftmembers are further moveable toward each other to at least one of aplurality of positions corresponding to a specific closing force betweenthe jaw members; each of said jaw members including an electricallyconductive sealing surface for communicating electrosurgical energythrough tissue held therebetween; at least one of the jaw membersincluding a cutting slot defined along a length thereof, the cuttingslot configured to accommodate reciprocation of a cutting instrumenttherethrough, the cutting instrument configured to engage at least aportion of the pivot to inhibit reciprocation of the cutting instrumentthrough the cutting slot; an actuator operably coupled to one of thefirst and second shaft members for selectively advancing the cuttinginstrument from a first position wherein the cutting instrument isdisposed proximal to tissue held between the jaw members to at least onesubsequent position wherein the cutting instrument is disposed distal totissue held between the jaw members, wherein the cutting instrument isadvanced from the first position to the at least one subsequent positionat an angle relative to a longitudinal axis defined by at least one ofthe shaft members.